The present invention relates generally to motor vehicle propeller shafts, and more particularly to an apparatus capable of minimizing the transfer of crash load and/or absorbing energy within a propeller shaft of a motor vehicle.
Propeller shafts are commonly used in motor vehicle propulsion. The multi-piece propeller shaft is used when larger distances exist between a front drive unit and the rear axle of the vehicle. The multi-piece propeller shaft transmits torque from the front drive unit to a rear axle. The multi-piece propeller shafts are typically supported by a center-bearing and corresponding support bracket. The center-bearing and support bracket support the center of the propeller shaft while still allowing the drive shaft to rotate and transfer mechanical energy from the front drive unit to the rear axle.
Besides transferring mechanical energy, it is desirable for propeller shafts to have adequate crashworthiness, be lightweight, and be easy and inexpensive to manufacture. In regards to crashworthiness, it is desirable for the propeller shaft to be capable of collapsing axially to prevent it from buckling, penetrating the passenger compartment, or damaging other vehicle components in close proximity to the propeller shaft. In some design scenarios, it may be desirable for the shaft to absorb a considerable amount of the deformation energy. In other design scenarios, the ability to collapse under very low loading may be a greater priority.
The amount of deformation energy absorbed, or the amount of energy required to initiate the collapse of the propeller shaft, can have an impact on the vehicle design and performance. Modern vehicles are purposely designed with crumple zones that allow the vehicle to absorb energy during collisions to prevent the transfer of such damaging energy to the vehicle occupants while attempting to preserve the integrity of the passenger compartment. The amount of energy required to axially collapse the propeller shaft, and the amount absorbed while collapsing can have an influence on how the crumple zones perform during collision.
Present crash features often utilize independent elements that deform to allow the propeller shaft to collapse under certain loading conditions. These independent elements often add to the complexity and cost of propeller shaft manufacture. They can also present design challenges when relatively low collision/collapse forces are desired while robust strength for normal usage is required. Finally, present collapsible features typically only provide a single resistive force profile in relation to a collision. Once the force necessary to effectuate collapse of the joint has been experienced, often relatively little additional collision energy is absorbed by the collapsing joint. Additional absorbed collision energy can result in beneficial safety and performance characteristics.
There is therefore a need for a collapsible two-piece propeller shaft that is capable of providing designers with the ability to control the collapsing force profile without adding to the complexity and cost of the velocity joint manufacturing. In addition, it would be highly desirable to have a collapsible two-piece propeller shaft capable of absorbing additional collision energy after the initial collapsing force has been realized. If the above improvements can be achieved, the safety of motor vehicles may be increased, the cost of manufacturing can be reduced, and an increase in the control over energy absorbed during collision may be realized.
Accordingly, an object of the present invention is to provide an improved propeller shaft assembly. An advantage of the present invention is that it provides improved crashworthiness, improved control over collision energy absorption, and is easier to manufacture than existing propeller shaft assemblies.
In accordance with the objects of the present invention, a propeller shaft assembly for a vehicle is provided. The propeller shaft assembly includes a constant velocity universal joint in a propeller shaft of a motor vehicle connecting a drive unit to a rear axle gearbox. The constant velocity universal joint includes at least two articulatably connected shaft portions, a hollow shaft, and a connecting shaft. The hollow shaft is connected to an outer joint part that includes an outer race surface having an outer forward portion and an outer rearward portion. The connecting shaft is connected to an inner joint part that includes an inner race surface having an inner forward portion and an inner rearward portion. The connecting shaft also includes a recessed surface portion. A plurality of torque transmitting balls are held by a ball cage and each are guided in one pair of corresponding outer and inner race surfaces. The ball cage holds the torque transmitting balls in a plane when the torque transmitting balls are in communication with the inner race surface and the outer race surface. When the propeller shaft assembly is involved in a collision, the torque transmitting balls translate off the inner race surface and drop into the recessed surface portion to allow the connecting shaft to collapses into the hollow shaft.
One of several advantages of the present invention is that it may forcibly collapse within itself at low collision loads. Another advantage of the present invention is that it minimizes the number of components used as compared to conventional shaft assemblies, thereby reducing mass and imbalance of the vehicle propeller shaft. Reduced mass and imbalance improves quality, decreases noise and vibration, and reduces costs in production and manufacturing of the propeller shaft.
The present invention itself, together with further objects and attendant advantages, will be best understood by reference to the following detailed description, taken in conjunction with the accompanying drawings.